As a method of analyzing samples, such as bloods, proteins and medicines, a technology using a microchip is well-known. Microchips have a minute flow channel, and a sample is caused to travel the minute flow channel by electrophoresis or capillary force, for example. When such a microchip is used, a cell provided in the minute flow channel or the halfway thereof is irradiated with light and the light through the minute flow channel or the cell is detected to analyze the sample. As optical analysis, absorptiometric method, fluorometry, etc., are known.
In order to improve the measurement accuracy of the optical analyzing method, it is necessary to eliminate internal stray light which is caused by aberration of lenses that configure an optical system and irregular reflection (excessive light which does not contribute to the measurement). For this reason, in the analyzing apparatus, unnecessary light is blocked by disposing an aperture on an optical axis.
As a method of blocking unnecessary light, for analytical tools like microchips, it has been proposed to form a tapered surface on a transparent member which configures a measurement cell. The tapered surface is for causing emitted light to scatter or reflect, and for allowing only light flux which has passed through the cell to reach a light receiving member.
However, according to the method of forming the tapered surface to block unnecessary light, it is difficult to cope with further advancement of refinement in μ-TAS (Micro Total Analysis System). That is, according to the structure that detaches/attaches the microchip to a specific observation point in the analyzing apparatus, positioning of the microchip to a precise location is restricted.
For example, when the microchip is detached/attached to the concave portion of a tray provided in the analyzing apparatus, it is necessary that the aperture size of the concave portion has some margin in consideration of a dimensional error of the microchip. Therefore, the precision of positioning the microchip can be ensured to some level, but because the microchip is not precisely set at a specific location, when the flow channel is made minute, it is difficult to make the observation point of the microchip and the optical axis precisely aligned with each other.
In order to make such alignment precise, for example, the dimensional precision of the microchip and that of the tray may be made strict and engagement of the microchip with the tray may be made strict, but in this case, the production cost increases. Moreover, a structure for an alignment using a positioning mechanism may be possible, but the apparatus becomes complex and expensive.
Patent Literature 1: U.S. Pat. No. 4,511,798
Patent Literature 2: Unexamined Japanese Patent Application KOKAI Publication No. 2007-298474